Kimberlite

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Kimberlite is an igneous rock best known for sometimes containing diamonds. It is named after the town of Kimberley in South Africa, where the first diamonds were found in this type of rock. Kimberlite occurs in the Earth's crust in vertical structures known as kimberlite pipes, as well as in igneous dikes and sills.

Formation and Composition

Kimberlite is formed deep within the Earth's mantle at depths between 150 and 450 kilometers. It is brought to the surface through volcanic eruptions that are extremely explosive due to the high gas content and rapid ascent of the magma. The rock is composed of a variety of minerals, including olivine, phlogopite, pyroxene, and garnet. Kimberlite also contains a significant amount of volatiles such as carbon dioxide and water.

Types of Kimberlite

There are two main types of kimberlite:

• **Group I Kimberlite**: Also known as "basaltic kimberlite," it is rich in magnesium and iron.
• **Group II Kimberlite**: Also known as "micaceous kimberlite," it contains more mica and is less common than Group I.

Economic Importance

Kimberlite is economically significant because it is the primary source of natural diamonds. The diamonds are formed under high-pressure, high-temperature conditions in the mantle and are carried to the surface by the kimberlite magma. Major diamond mines around the world, such as those in Botswana, Russia, and Canada, are located in kimberlite pipes.

Geological Features

Kimberlite pipes are carrot-shaped, vertical intrusions that can extend deep into the Earth's crust. They are often found in clusters and can vary significantly in size. The surface expression of a kimberlite pipe is typically a small, circular depression known as a "diatreme."

Exploration and Mining

Exploration for kimberlite involves geological surveys, sampling, and drilling. Once a kimberlite pipe is discovered, it is evaluated for its diamond content. Mining methods include open-pit mining and underground mining, depending on the depth and size of the kimberlite pipe.

Notable Kimberlite Locations

• Kimberley, South Africa
• Ekati Diamond Mine, Canada
• Mir Mine, Russia
• Jwaneng Diamond Mine, Botswana

See Also

• Diamond
• Volcanic pipe
• Igneous rock
• Mantle (geology)
• Geology